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GC804 Combustible Gas Detector

Product Literature

  • Intelligent Model Combustible Gas Detector
  • Catalytic Sensor
  • LCD Display
  • 4-20mA output
  • Relay Contacts
  • 2 Alarm Set Points
  • Explosion-proof
  • Aluminum or Stainless Steel housing

Keywords:  Combustible Gas Detector, Flammable Gas Detector, Hydrocarbon Gas Detector, Methane Detector, Butane Detector, Propane Detector, Hydrogen Detector, Catalytic Gas Detector, Catalytic Sensor

Features and Benefits

  • A stand-alone, explosion-proof, catalytic combustible gas detector
  • 4-20 mA output for connection to external equipment
  • Two alarm set points with voltage-free contact relay outputs for local control
  • Bright LCD display of gas concentration in % LEL
  • Reliable, easy to install. simple to maintain and operate
  • The catalytic sensor responds to all hydrocarbon combustible gases
  • The sensor can be calibrated to specific combustible gases such as methane, propane, butane, hydrogen, gasoline, ethanol, and other combustible gases and vapors
  • Epoxy coated copper-free aluminum housing
  • Explosion-proof approved housing for Class I, Group A, B, C, D
  • Shipped fully assembled and pre-calibrated
  • Installed and fully operational in less than 1 hour
  • Magnetic switch initiates test or calibration sequence
  • On-screen calibration instructions insure error-free results
  • Available up to IP66 rating
  • Available with wireless transmitter as an accessory with text, e-mail notifications feature
  • 5 Year Warranty
  • Made in the USA
  • Optional remote sensor available for mounting in hard to reach places and high ceilings
  • Sensor can be installed to monitor air flowing through duct with the optional duct mounting accessory
  • Please see datasheet for ordering information

Product Summary

Our latest new and improved intelligent model combustible gas detector is now available in both aluminum and stainless steel and is approved for Class I, Group A, B, C, D.  We have packaged the detector in a more compact housing which is lighter than previous models and features a a catalytic sensor, a bright LCD screen which displays the gas concentration in % LEL, 4-20 mA output, dry contact relays, and on-screen calibration instruction.  The gas detector responds to all hydrocarbon combustible gases such as methane, propane, butane, hydrogen, gasoline (petrol), acetone; ethanol, toluene, and other gases.  Available with optional wireless transmitter with text, e-mail notifications feature.  5 Year Warranty.  Made in the U.S.A.


Use the NOVA-Sensor ELITE Combustible Gas Detector to alert personnel when a flammable gas or vapor is accumulating in a protected area. This detector uses a catalytic poison-resistant sensing element, and provides accurate measurements in atmospheres where traces of silicone or other poisoning agents may be present. Readings are unaffected by humidity or carbon dioxide.

The display screen on the NOVA-Sensor ELITE continuously displays operating status and the actual concentration of gas in percentage of the Lower Explosive Limit (%LEL). This reading is converted to a standard 4-20 mA signal, which may be connected to any remote device for remote display or logging. Relay contacts are provided which transfer when the gas concentration exceeds the LOW ALARM and HIGH ALARM set points. Typical set points are adjusted by the installer upon installation and may be reset later by authorized personnel. The relays are suitable for controlling local HVAC equipment, alarm signal devices or for equipment shutdown. Fault relay contacts are also available which operate upon loss of power or internal failure of the unit.

The automatic calibration sequence is initiated by using a magnetic key on the top portion of the enclosure. During calibration, step-by-step instructions are displayed on the NOVA-Sensor ELITE screen. There are no screwdriver or other manual adjustments required, and the calibration can be performed even in the presence of combustible gases.

Typical gases for pre-calibrated NOVASensor ELITE Combustible Gas Detectors include:

Methane (CH4)
Iso Propyl Alcohol
Methyl Ethyl Ketone
Ethyl Acetate
Gasoline (Petrol)


Combustible gas sensing capability shall be provided by poison-resistant catalytic gas sensors, contained in explosion proof housings. The sensor shall include a microprocessor based control electronics which converts the measured gas concentration in percent LEL to the industry standard 4-20 mA signal, plus alarm and fault relay outputs. A continuously reading digital display shall be provided on the sensor, capable of displaying sensor status in the current LEL reading. A switch for initiating sensor calibration shall be provided. Calibration shall not require any operator adjustment. All calibration data shall be stored in non-volatile memory in the sensor. Relay and analog outputs shall normally be inhibited during calibration; however, it shall be possible for the calibrating technician to selectively enable outputs when desired. The sensor shall be suitable for offshore use, and the manufacturers data shall so state. Safety Systems Technology Model GC804 Combustible Gas NOVA-Sensor ELITE, or approved equivalent, shall be supplied.

One Channel Combustible Gas Sampling System

A complete and fully assembled gas sampling system which uses customer supplied instrument air to create a vacuum which extracts the sample gas from the source and passes through a sampling block and through the gas sensor.  The system is custom built in a non-metallic NEMA4 enclosure with all the components required to extract the gas sample and check the level of combustible gas present.  The system includes a built-in NOVA-Sensor ELITE controller with bright LCD display of gas concentration in % LEL, a gas sampling block, combustible gas sensor, sensor calibration switch, 24V DC power supply, a flow meter with integral pressure regulator, filter/regulator for instrument air, vacuum eductor, filter with liquid drain for sample, 3-way brass ball valve for calibrating gas, ¼ inch tubing, and tube fittings.   Optional accessories available include a drain solenoid controller for automatic liquid drain, drain solenoid valve and heater.  The heater is supplied as an optional accessory to prevent condensation within the unit for outdoor applications.

The system is pre-calibrated and delivered ready to install.  Simply connect power, air, and tubing from the area being monitored.

For applications which require monitoring of multiple gases, the system can be custom designed to monitor any combination of combustible, toxic, and oxygen simultaneously.

One Channel Combustible Gas Sampling System

Technical Specifications and Ordering Information

Technical Specifications

Sensor Type: Catalytic bead with excellent long term zero and sensitivity stability
Poison Resistance: Highly resistant
Gases Detected: Most combustible gases and vapors
Sensor Life: Typical 5+ years
Measuring Ranges: 0-100% LEL
Accuracy: +/- 1% LEL (CH4)
Zero Drift: < +/- 1/2 mV/month
Linearity: Effectively linear to 100% LEL (to within 5%)
Response Time: T90 < 30 seconds
Modes: Normal operation, set-points, calibration, set-up
Warranty: 5 years
Approvals: Explosion-proof approved housing
Class I, Division I, Groups A, B, C, D; Class I Zone I, AEx d IIC; Type 4X
ATEX:  II 2G Ex d IIC Gb
Electrical Specifications
Input Power: 24 VDC nominal, 16 to 32 VDC
92 mA standby, 120 mA alarm
Relay Contact Ratings: 6 amps @ 28 VDC or 300 VAC resistive
1/8 HP @ 120/240 VAC
Analog Signal: 0-20 mA (600 Ohms or less)
0 mA  Malfunction
4 mA  Setup Mode/Calibrate
4 mA  Zero Reading
4-20 mA  0-100% LEL
> 20 mA  Over-range
Display: Graphic Liquid Crystal Display
Displays target gas concentration in % LEL
Flashing screen in alarm mode
Low brightness setting in power save mode
Field Connections: 4-20 mA output – three wire shielded cable
All other connections 22 AWG (.35mm2) to 12 AWG (4.0mm2)
Wireless Communication: Available with optional wireless transmitter with text, e-mail notification features
Environmental Specifications
Operating Temperature: Electronics -40°F to 185°F (-40°C to 85°C)
Sensor -40°F to 266°F (-40°C to 130°C)
Operating Humidity: 0-100% RH, non-condensing
Ingress Protection: IP40 to IP66
Mechanical Specifications
Dimensions: 6.4 x 5.7 x 4.3 inches
(163 x 145 x 109 min)
Weight: 4.0 lbs (1.8 kg) Aluminum;
10.0 lbs (4.5 kg) Stainless Steel
Controller Housing: Aluminum or Stainless Steel
Sensor Housing: Stainless Steel

Ordering Information

804-4-AL Model GC804 NOVA-SensorElite™ Combustible Gas Detector in aluminum housing with sensing head
804-4-SS Model GC804 NOVA-SensorElite™ Combustible Gas Detector in stainless steel housing with sensing head
851-1-4 Rain shield, stainless steel (IP65)
851-5-4 Water spray shield (for IP66, requires 852-1-4)
852-1-4 Dust cover, stainless steel (requires 851-1-4)
854-1-4 Duct mount, stainless steel
859-1-4 Gas sensor collection cone, stainless steel
867 Complete calibration kit
10121 Spare calibration / test key
804-2-AL Aluminum enclosure w/ optional sensor in stainless steel, CSA & ATEX listed
804-2-SS Stainless steel enclosure w/ optional sensor in stainless steel, CSA & ATEX listed